Hitherto, in a liquid crystal display device, a light-guiding plate, for example, has a light source disposed on a side thereof, has a liquid crystal conversion element mounted on an upper surface thereof, and is used for guiding light, which is radiated from the light source, to a liquid crystal display element.
Here, the light-guiding plate has undergone a treatment such as printing or embossing on a surface opposite to the display surface (light-exiting surface) as shown, for example, in FIG. 11. Then, the light radiated from the light source is scattered at this opposite surface, and only the light that has escaped from the total reflection angle among this scattered light exits from the light-exiting surface. In other words, the light that was unable to escape from the total reflection angle among the scattered light is reflected at the light-exiting surface instead of exiting from the light-exiting surface. Moreover, not all the light that has escaped from the total reflection angle exits at the light-exiting surface. Much of the light is reflected at the light-exiting surface and returns to the inside. In other words, the light that can exit from the light-exiting surface is a component of a slight amount which is a part of the light that has escaped from the total reflection angle among the light that has been scattered at the opposite surface by hitting the printing or embossing. As a result of this, the light is damped due to lengthened optical path by repetition of such reflection till the light exits, thereby raising a problem in that the light from the light source cannot be utilized sufficiently.
Further, in view of the aforesaid problem, there is one in which a light-emitting sheet having a plurality of protrusions is bonded to a surface of a light guide so that the protrusions thereof may be brought into point contact (For example, Japanese Laid-open Patent Publication No. 2000-249836 and Japanese Laid-open Patent Publication No. 2000-338507). In such a light-guiding plate, the light from a light source is introduced into a light-emitting sheet from a light guide via the point contact part, and exits from the light-exiting surface. Now, even in the one disclosed in the patent document 1, the light that cannot escape from the total reflection angle repeats being reflected within the light-emitting sheet, so that the light from the light source cannot be utilized sufficiently. Moreover, in exiting from the light-exiting surface, the light must pass through the point contact part. Since the point contact imposes a fineness limit to the area of the part that can be passed through, the light cannot enter the light-exiting surface and much of the light repeats being reflected in the light guide, so that the problem of the loss of light is not sufficiently solved.